A radius discrepancy is known to exist for late-type dwarfs in the sense that they have larger radii and lower \(T_{\rm eff}\) s than predicted by stellar theory [1]}, [2]}, [3]}, [4]}, [5]}. This has been attributed to the inhibition of convection [6]}, [7]} due to magnetic fields and/or starspots. There is evidence that stars in short-period binaries are affected in a qualitatively different way [6]} because tidal effects cause them to rotate more quickly and thus show stronger activity. However, the radius discrepancy has also been found in longer-period binaries [9]} and single stars [1]}, [3]}, and there are also examples of stars in short-period binaries that do not show the discepancy [12]}, [13]}, [14]}. Recent analyses have found a large scatter in the size of the radius discrepancy between and even within binary systems [15]}, [16]}. Under the assumption that the age and metallicity of the ZZ UMa system can be inferred from the properties of star A, the poor agreement between theoretical models and the measured properties of star B make it an excellent candidate for a star showing the radius discrepancy. ZZ UMa B is another example of a star in the region of 1\(~{\rm M}_\odot \)  showing the radius discrepancy.
